my buddies 86Gt went 12.42 this past weekend it has a intake, cam and a vortech v3 si trim and he has 373 gears with 275/50r15 bfg dr's and he is having to shift into fifth before getting down the track...so what needs to happen should he go with a taller tire or change gear ratio any suggestions would be great thanks n advance
what to change tires or gears??
- Thread starter daviszx3
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Beasty306GT
Active Member
Well, go out and measure the total height of the tires he's running now...really we should all know that before we make any suggestions. I'm gonna say it's around 26 inches or so...i'm no expert on this subject but he should probably look for something around 27-28 inches tall. I'm sure someone with more slick/drag radial experience than me will chime in on tire height. This is something that i could also benefit from and i bet i'd be faster with the right size tires.
A taller tire will have the benefit of more contact patch, which translates to better traction, all else equal.
25thmustang
Mustang Master
something is definitly wrong there, see what happens if he shifts at 6k, 113 isnt a very high trap speed to be maxing out 4th gear.
Is he using the stock tach? cause when my stock tach reads 7k its at around 6000-6200 on my autometer
Is he using the stock tach? cause when my stock tach reads 7k its at around 6000-6200 on my autometer
Weird. I very nearly ran out of RPM's before the traps on my notch with stock H/C/I, stock-sized tires, T-5, cat'ed X-pipe, stock 10* timing, and 4.10's - trapping 15.0 @ 98 MPH, shifting at 5600 RPM. 
Then again, I granny-shift like a geezer and the worn-out mostly stock suspension can't hook off the line for diddly, so ... yeah.
Then again, I granny-shift like a geezer and the worn-out mostly stock suspension can't hook off the line for diddly, so ... yeah.
25thmustang
Mustang Master
Are we talking running out of gear meaning he is hitting the 6250 rev limiter, or meaning he is at 5500 and afraid to take it higher?
Our 4.10 equipped car traps 111 and still has RPM left.
Our 4.10 equipped car traps 111 and still has RPM left.
blackened88lx
Active Member
Something's definitely wrong. He must just be afraid to turn it any higher?? One friend went 122mph with 4.10s and another went 119 with 3.73s, not running out of gear.
blackened88lx
Active Member
axeman
Founding Member
Maybe he should try running it out before changing anything. Chances are his tach is not reading correctly. I haven't been to the track in a while, but I've run some of my best times without even looking at the tach, just going by feel. I highly doubt there are many stock tachs that do read correctly. If he's afraid of breaking anything, maybe he shouldn't be racing.
Guess that was my problem, too. I'm afraid to explore that danger zone above 5500 RPM at all. Hell, I don't even rev teh Notch above 4k but maybe once in a blue moon ... but then, with stock H/C/I, I really don't have any high-RPM power to speak of, so there's really no point I can see in shooting for 6k.
Again, I'd recommend changing tires instead of gears - way easier, probably cheaper. If you throw 'em on a spare set of rims and don't like the results (need taller/shorter tires), then you can always swap back to your stockers, sell off those tires, and throw on another pair - WAY more convenient than having to pull axles and fart around with pinion angles and stinky gear fluid and whatnot.
Again, I'd recommend changing tires instead of gears - way easier, probably cheaper. If you throw 'em on a spare set of rims and don't like the results (need taller/shorter tires), then you can always swap back to your stockers, sell off those tires, and throw on another pair - WAY more convenient than having to pull axles and fart around with pinion angles and stinky gear fluid and whatnot.
